Add authz validation for courses.manage_pages_and_resources to ProctoredExamSettingsView #443

Description

On the backend side, the ProctoredExamSettingsView (handling both GET and POST requests) currently lacks authorization validation. It needs to be updated to enforce the courses.view_pages_and_resources permission for GET requests, and the courses.manage_pages_and_resources permission for POST requests. This will secure the endpoint and bring it in line with its sibling view, ProctoringErrorsView (used for the advanced settings page), which already implements the correct authorization checks.

Expected Behavior

When a user makes a request to the ProctoredExamSettingsView endpoint, the backend should verify if the user has the appropriate permission based on the HTTP method:

• GET requests: Verify the courses.view_pages_and_resources permission.
• POST requests: Verify the courses.manage_pages_and_resources permission.

If they have the required permission, the request should proceed normally. If they do not, the backend must block the request and return an HTTP 403 Forbidden error.

Current Behavior

ProctoredExamSettingsView is missing the authz validation check. Because of this, a user who lacks the proper permissions could potentially access (missing courses.view_pages_and_resources) or modify (missing courses.manage_pages_and_resources) the proctored exam settings by bypassing the UI and making direct API calls (GET or POST) to this endpoint.